Process for exact electrochemical working of workpieces of different shape

ABSTRACT

Working of workpieces by the electrochemical method, which workpieces have surfaces inclined with respect to the direction of relative advance of tool to workpiece. At least one of the working parameters, such as voltage, conductivity of the electrolyte, surface of electrode, and/or time of working is adjusted with respect to the parameter applied for working of surfaces perpendicular to the direction of relative advance of tool and workpiece.

ilite States Patent [191 Zubak Nov. 19, 1974 PROCESS FOR EXACT ELECTROCHEMICAL WORKING OF WORKPIECES OF DIFFERENT SHAPE [75] Inventor: Jan Zubak, Ostrov, Czechoslovakia [73] Assignee: Vyskumny ustav Automatizacie a mechanizacie, Nove Mesto nad Vahom, Czechoslovakia 22 Filed: on. 15, 1971 21 Appl. No; 189,634

[30] Foreign Application Priority Data Dec. 8, 1970 Czechoslovakia 8247/70 [52] US. Cl. 204/l29.25, 204/224 M [51] Int. Cl B231) l/l4, 323p 1/04 [58] Field of Search 204/1291, 129.2, 129.25, 204/1295, 129.55

[56] References Cited UNITED STATES PATENTS 3,075,902 l/1963 Bradley et a1 204/1292 3,372,099 3/1968 Clifford .1 204/1292 3,580,827 5/1971 Lannegrace 204/l29.25

3,630,878 12/1971 Haggerty 204/225 FOREIGN PATENTS OR APPLICATIONS 42-17414 9/1967 Japan 204/12925 OTHER PUBLICATIONS Electrochemical Machining by De Barr et al., pp. 158, 159, Pub. by American Elseview, New York, 1968. Electrochemical Machining by De Barr et al., pp. 67, pub. by American Elseyi er Pub, Co., liey York, 1968. q

Primary Examiner-F. C. Edmundson Attorney, Agent, or Firm-Murray Schaffer [5 7] ABSTRACT Working of workpieces by the electrochemical method, which workpieces have surfaces inclined with respect to the direction of relative advance of tool to workpiece. At least one of the working parameters, such as voltage, conductivity of the electrolyte, surface of electrode, and/or time of working is adjusted with respect to the parameter applied for working of surfaces perpendicular to the direction of relative advance of tool and workpiece.

6 Claims, 5 Drawing Figures FROCESS FOR EXACT ELECTROCHEIVHCAL WORKING OF WORKPIECES OF DIFFERENT SHAPE BACKGROUND OF THE INVENTION This invention relates to a process for accurate electrochemical working of workpieces of different shape.

The electrochemical working of workpieces of different shape as performed according to actually known methods lacks the required accuracy. An accurate shape of the workpiece corresponding to the shape of the tool is in particular not achieved, if some portion of the worked surface of the workpiece is inclined with respect to the direction of the relative advance of tool and workpiece. When working such inclined objects, a gap corresponding to the condition of equilibrium is created between the tool and the workpiece. This gap achieves different magnitudes, wherein the actual gap between surfaces perpendicular to the advance is smaller than the actual gap between surfaces which are inclined with respect to the relative advance of tool and workpiece. The consequence thereof is, that the tool does not fit exactly into the workpiece after the piece is finished and gaps are always left at the lateral surfaces. In the known techniques, in order to improve the accuracy of working, the magnitude of the working gap has been reduced to the utmost. Even so the required accuracy has not been achieved. In order to achieve an accurate shape of the product, the prior art has resorted to complicated and troublesome corrections of the tool and/or of the working electrode. Consequently, the working electrode actually is made with a shape different from that of the finished workpiece. Concomitantly in order to achieve an accurate shape of the product, all of the working parameters for which these corrections have been made must be strictly maintained. It is an object of this invention to provide a method of electrochemical working of workpieces, where the workpiece would be to a high degree a mirror image of the working tool.

It is a further object of this invention to provide a method of electrochemical working of workpieces, where any troublesome corrections of the working tool would be eliminated.

It is another object of this invention to provide a method of electrochemical working of workpieces, which would allow variations of at least some of the working parameters without affecting the accuracy of the workpiece.

It is still another object to provide arrangements, which would allow this method to be applied to existing machinery without complicated additional means.

SUMMARY OF INVENTION According to this invention, a method is provided for the electrochemical working of pieces in which for surfaces of the tool, which are inclined at a constant or variable angle different from a right angle with respect to the direction of the relative advance of tool and workpiece, at least one of the working parameters is adjusted such as the voltage, the conductivity of the electrolyte, the surface of the working electrode, and- /or the time of working with respect to those parameters for working of surfaces which are perpendicular to the relative advance of tool and workpiece.

Other features and advantages of this invention and different embodiments thereof will be apparent from the following description with reference to the drawmgs.

DESCRIPTION OF DRAWINGS In the attached drawings FIG. 1 shows those conditions occurring in the course of electrochemical working of two surfaces, one of which is perpendicular, the other at an acute angle with respect to the relative advance of tool and workpiece.

FIG. 2 is a similar view, indicating those conditions occurring, where the lateral surface is worked for a limited time with respect to the front surface.

FIG. 3 shows in axial cross section the adjustment of the working electrode either by changing its voltage or by using different times of working,

FIG. 4 an axial cross section of a rotating conical working electrode, parts of the surfaces of which are mutually electrically isolated,

FIG. 5 indicates in axial cross section adjustments of a working electrode achieving changes of conductivity of the electrolyte in the working gap.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, it will be seen that if it is desired to achieve after completion of working the exact shape in the workpiece of the working tool, the working gap between tool and workpiece at surfaces which are inclined at a certain or determined angle with respect to the direction of relative advance of tool and workpiece must have a certain magnitude with respect to the magnitude of the working gap of surfaces which are perpendicular to this direction, namely d d Sin a d d /sin a it is obvious that some of the working parameters must be correspondingly adjusted, if surfaces having different inclinations with respect to the direction of relative advance of tool and workpiece have to be worked properly. If we include the working parameters into equation (2) we obtain 11,, d /sin a E.H. Vsp/Ve sin a E.H/8 sin a E.H.S/I.sin a (3) where E is the voltage between tool and workpiece H the conductivity of the electrolyte Vsp the specific removal of material S the surface of the electrode I the working current Ve speed of advance between tool and workpiece. If conditions of equation (I) have to be fulfilled d E.H.S/T.sin a sin a d sin a From equation (4) follows, that if we want to obtain an exact shape of the workpiece for electrochemical working on surfaces inclined-at a certain angle with respect to the direction of relative advance between tool and workpiece, some of the working parameters have to be adjusted such as the voltage E, the conductivity H, or the surface S to parameters E H S so that E E.sin a or H H.sin a or S S.sin a 5 If we proceed with the working according to this invention so that the working electrode advances with respect to the workpiece at the speed Ve (see FIG. 2) a layer a of material is removed from the surface perpendicular to this direction within the time t equal to a=Ve.t

The relative advance of the working electrode with respect to the workpiece for the inclined surface is however Vn and within the time t, a layer a, is removed If we want to meet the conditions stipulated in equation l the speed of removal of material on the lateral inclined surface should be Vn Ve/sin a and (8) a, a.sin a'= Vn.t Ve/sin a t, and t =a.sin a/Vn Ve t sin a/Ve =t sin a 9 From equation (9) it follows, that the same result of an accurate shape can be achieved by adjustment of the working time of the working current on the surface inclined with respect to the direction of advance to the time t The chosen time interval cannot, of course be chosen arbitrarily, but must be generally lower or equal to the time, for which the working gap between surfaces perpendicular to this relative advance are reduced by one half, so that t dc/2Ve 60 sec a good flooding of the working gap by the electrolyte is safeguarded and no contact of the working electrode with the worked material takes place. It is selfunderstood, that in case working proceeds with large gaps, this time interval may be correspondingly larger.

The working electrode for electrochemical working according to this invention has to be adjusted according to the working parameter, which is to be selected for adjusting.

In FIG. 3 a working electrode 1 is shown suitable for adjustment of the voltage E for example. The current is supplied directly on to the stern part of the electrode 1 which has a face working the front surface of the workpiece. The electrode 1 includes side parts 2 and 2a the faces of which are at acute angles to the front face of the electrode and to the direction of travel. The parts 2 and 2a are secured to the electrode stem but are electrically insulated therefrom. Current is supplied to each of the parts separately by respective resistors R and R which are connected to the stem part of the electrode 1 to which the current has already been supplied. In the alternative these parts 2 and 2a may be connected to another independent source of current of a suitable voltage to comply with the conditions E1, E2 E.Sin a1, E Sin 0L2.

A less pretentious or complex method is to connect the individual parts of the working electrode 1 to the same source of current via a time switch (not shown on the drawing) which is adjusted to switch on different parts of the electrode for a certain time interval t so that t t min a t.sin a where working electrodes of rotational shape can be used, such as conical or spherical shapes or of disk shape, and it will be most advantageous to reduce parts of the working surface so as to comply with the condition S S S I S.sin a S.sin bz and to impart to the electrode a simultaneous rotating motion. After this adjustment the adjusted parameter remains stable and cannot be changed and therefore the working accuracy is not influenced by any changes of the remaining parameters.

These conditions are for instance met by using a working electrode 1 as shown in FIG. 4, where a part 5 of its circumference is electrically isolated for instance by polyethylene coating, so that only part 4 of the inclined surface takes part in the working. In this case the working surface, of the rotating working electrode, can be divided into two or more, but al least to two, parts, one isolated and one not isolated. Such an arrangement of the working electrode is particularly suitable for shapes with variable inclination of the surface, for instance for spherical surfaces.

If the workpiece has lateral walls at a constant or slightly differing angle 0:, changes of conductivity of the electrolyte can be advantageously utilized for this purpose. An advantage of this method is, that the conductivity can be varied in a simple manner within wide limits. It is of course selfunderstood that in order to achieve accurate results, the conductivity H must be equal to H.sin a. An example of an embodiment of this method is indicated in FIG. 5, where the conductivity of the electrolyte can be either arbitrarily changed or maintained at an exact value. A channel 6 is provided in the center of this working electrode 1, through which channel 6 the liquid working electrolyte having the conductivity H passes at a predetermined overpressure p in an amount of Q liters per minute into the interelectrode space, i.e., into the working gap 7.'Pressurized air at an overpressure p at the amount of Q liters per minute is supplied by way of the opening 8 laterally of the channel 6. The opening 8 terminates into the working gap 7 via a narrow slot 9 (about 0.05 to 0.1 mm). The working electrolyte flowing through the channel 6 at the center of the working electrode 1 has a pressure about 2 to 8 kp higher that the pressure of air, so that its passage is safeguarded. Both parts of the working electrode are mutually electrically connected and supplied from a common source of current. The

exact shape of the workpiece is thereafter obtained solely by maintenance of the correct relation of both components, passing through the working gap 7 so that (Q /Q (1.5 sin oz/l-sin a) The method of accurate electrochemical working according to this invention safeguards the accuracy of the product according to the shape of the working electrode without corrections of its shape. According to the present method of electrochemical working the magnitude of the lateral gap for adjustment of one of the working parameters is dependent on the magnitude of the front working gap. Only the ratio of these parameters needs to be checked, or permanently adjusted. Whereafter the remaining working parameters may be varied within wide limits without influencing the accuracy of working. If for instance the workpiece is worked with a disk shaped working electrode, where the angle a of inclination with respect to the relative advance of tool and workpiece is 30, then the magnitude of the active electrode surface S S. sin a 100% =1 0.25 100%= 25%. The remaining electrically isolated space SSsin a is 75%. In case any of the parameters E, H, Ve, Vsp, is changed then the magnitude of the front gap is changed, or the speed of working, but the accuracy of working remains the same as simultaneously the magnitude of the lateral gap changes so that d sin a.

I claim:

1. A process for electrochemically working a workpiece using an electrode tool moving relatively thereto, wherein said workpiece is finished to the shape of said tool having a portion of its surface perpendicular to the relative direction of movement and a portion of its surface inclined at an angle to the relative direction of movement, comprising the steps of introducing an electrolyte between said tool and said workpiece and applying a current across said electrolyte, the improvement comprising adjusting, with respect to the surface inclined to the perpendicular surface at least one of the following parameters, the applied voltage, the conductivity of the electrolyte, the surface of the electrode tool or the time of working so that the ratio of said adjusted parameter to the corresponding parameter with respect to the surface perpendicular to the relative direction of movement is equal to sin of the angle which said inclined surface makes with the relative direction of movement.

2. A process for accurate electrochemical working as set forth in claim 1, where for individual surfaces of the working electrode inclined at a certain angle with respect to the direction of relative advance of tool and workpiece current is supplied solely for a certain part t, of the corresponding time t of working of a surface perpendicular to said direction of advance, the time t of working the inclined surface being not longer than the time, in the course of which the working gap for working a surface perpendicular to said direction of advance is reduced for one half, so that t d /Ve seconds and t, t sin a d /2Ve 60 sin :1 seconds where d is the width of the front gap between tool and workpiece for a surface perpendicular to the direction of relative advance between tool and workpiece Ve the speed of this relative advance. 3. The process according to claim 1 wherein E,=E. sin a, H =H. sin a, T T. sin a, S S. sin 0: wherein E, H, T and S are the voltage, conductivity time and surface parameters with respect to the perpendicular surface, E H T and S are the corresponding parameters at the inclined surface, and a is the value of the angle the inclined surface makes with the relative direction of movement.

4. The process according to claim 1 including the step of varying said adjustment during working to correspond to variances in the surface of said workpiece.

5. The process according to claim 1 wherein said workpiece has a plurality of inclined surfaces extending at different angles to the direction of movement of said electrode tool and wherein different voltages are applied to selected sections corresponding to the respective inclined surface.

6. The process according to claim 1 wherein said tool has a plurality of surfaces meeting at different angles with respect to the direction of movement of tool and workpiece, the step of adjusting the conductivity of said electrolyte comprising supplying pressurized air so that the ratio of the pressure of the supplied electrolyte to the pressure of air is (Qz/Q 1.5 sin all sin a) 2 wherein Q, is the amount of air pressure and Q is the amount of electrolyte pressure. 

1. A PROCESS FOR ELECTROCHEMICALLY WORKING A WORKPIECE USING AN ELETRODE TOOL MOVING RELATIVELY THERETO, WHENIN SAID WORKPIECE IS FINISHED TO THE SHAPE OF SAID TOOL HAVING A PORTION OF ITS SURFACE PREPENDICULR TO THE RELATIVE DIRECTION OF MOVE MENT AND A PORTION OF ITS SURFACE INCLINDED AT AN ANGLE TO THE RELATIVE DIRECTION OF MOVEMENT, COMPRISING THE STEPS OF INTRODUCING AN ELECTROLYTE BETWEEN SAID TOOL AND SAID WORKPIECE AND APPLYING A CURRENT ACROSS SAID ELECTROLYTE, THE IMPROVEMENT COMPRISING ADADJUSTING, WITH RESPECT TO THE SURFACE INCLINED TO THE PREPENDICULAR SURFACE AT LEAST ONE OF THE FOLLOWING PARAMETERS, THE APPLIED VOLTAGE, THE CONDUCTIVITY OF THE ELECTROLYTE, THE SURFACE OF THE ELECTRODE TOOL OR TIME OF WORKING SO THAT THE RATIO OF SAID ADJUSTED PARAMETER TO THE CORRESPONDING PARAMETER WITH RESPECT TO THE SURFACE PERPENDICULAR TO THE RELATIVE DIRECTION OF MOVEMENT IS EQUAL TO SIN2 OF THE ANGLE WHICH SAID INCLINED SURFACE MAKES WITH THE RELATIVE DIRECTION OF MOVEMENT.
 2. A process for accurate electrochemical working as set forth in claim 1, where for individual surfaces of the working electrode inclined at a certain angle with respect to the direction of relative advance of tool and workpiece current is supplied solely for a certain part t1 of the corresponding time t of working of a surface perpendicular to said direction of advance, the time t1 of working the inclined surface being not longer than the time, in the course of which the working gap for working a surface perpendicular to said direction of advance is reduced for one half, so that t dc/Ve 60 seconds and t1 t . sin2 Alpha dc/2Ve 60 . sin2 Alpha seconds where dc is the width of the front gap between tool and workpiece for a surface perpendicular to the direction of relative advance between tool and workpiece Ve the speed of this relative advance.
 3. The process according to claim 1 wherein E1 E . sin2 Alpha , H1 H . sin2 Alpha , T1 T . sin2 Alpha , S1 S . sin2 Alpha wherein E, H, T and S are the voltage, conductivity time and surface parameters with respect to the perpendicular surface, E1, H1, T1 and S1 are the corresponding parameters at the inclined surface, and Alpha is the value of the angle the inclined surface makes with the relative direction of movement.
 4. The process according to claim 1 including the step of varying said adjustment during working to correspond to variances in the surface of said workpiece.
 5. The process according to claim 1 wherein said workpiece has a plurality of inclined surfaces extending at different angles to the direction of movement of said electrode tool and wherein different voltages are applied to selected sections corresponding to the respective inclined surface.
 6. The process according to claim 1 wherein said tool has a plurality of surfaces meeting at different angles with respect to the direction of movement of tool and workpiece, the step of adjusting the conductivity of said electrolyte comprising supplying pressurized air so that the ratio of the pressure of the supplied electrolyte to the pressure of air is (Q2/Q1) (1.5 . sin2 Alpha /1 - sin2 Alpha ) wherein Q1 is the amount of air pressure and Q2 is the amount of electrolyte pressure. 